Clinical and imaging characteristics of dementia in multiple system atrophy

Background: Recent reports show that dementia occurs in 5-26% of multiple system atrophy (MSA) patients. However, the structural or pathological correlates of dementia in MSA are unclear yet. Methods: Of 152 patients with MSA, 59 fulfilled the criteria of probable MSA and 9 (15%) had dementia. Six of those patients and 9 without dementia, in addition to 10 controls, were included. All subjects underwent clinical evaluation including UMSARS, neuropsychological examinations, 3T-MRI, and Pittsburgh Compound B (PIB) PET imaging. The cortical thickness was assessed using surface-based morphometry. Results: Age and disease duration were similar between MSA with dementia and without dementia, while motor disability was more severe in MSA with dementia. In neuropsychological tests, attention, visuospatial function, and language function were impaired in MSA with dementia. Mean PIB binding was similar among the three groups. Cortical thickness was reduced in precuneus/cuneus, uncus, and posterior cingulate in MSA with dementia compared to the controls, and in parahippocampal and lingual cortices compared to MSA without dementia. Conclusions: Dementia was found in 15% of the probable MSA patients, which was similar to those reported in previous studies. It appears that amyloid pathology has limited role in dementia in MSA, although some patients had increased cortical amyloid burden. Cortical thinning in MSA-D was observed in areas where cortical thinning was reported in Alzheimer disease or Parkinson disease dementia, but its pathological relevance is unclear. The neuropathological processes leading to the development of dementia in MSA appears to be multifactorial and heterogenous.